A steering apparatus for an automobile, as illustrated in FIG. 17, is constructed so that rotation of the steering wheel 1 is transmitted to an input shaft 3 of a steering gear unit 2, and as this input shaft 3 turns, the input shaft 3 pushes or pulls a pair of left and right tie rods 4, which apply a steering angle to the front wheels of the automobile. In order to accomplish this, the steering wheel 1 is fastened to and supported by the rear end section of a steering shaft 5, and this steering shaft 5 is inserted in the axial direction through a cylindrical shaped steering column 6, and is supported by this steering column 6 such that it can rotate freely. The front end section of the steering shaft 5 is connected to the rear end section of an intermediate shaft 8 via a universal joint 7, and the front end section of this intermediate shaft 8 is connected to the input shaft 3 via a different universal joint 9. The intermediate shaft 8 is constructed so that it can transmit the torque and it can contract over its entire length due to an impact load. Therefore, when the steering gear unit 2 is displaced in the backward direction due to a primary collision between an automobile and another automobile or the like, that displacement is absorbed, which prevents the steering wheel 1 from displacing in the backward direction via the steering shaft 5 and hitting the body of the driver.
In such a steering apparatus for an automobile, for providing additional protection of the driver, it is necessary to adopt a structure that allows the steering wheel 1 to displace forward while absorbing impact energy when an accident occurs. After the primary collision, a secondary collision occurs when the body of the driver collides with the steering wheel 1. As this kind of construction, construction is known (refer to JP51-121929(U), JP2005-219641(A), JP2000-6821(A), JP56-25981(U), and JP60-169365(A)) and widely used in which an energy absorbing member, which absorbs an impact load by plastically deforming, is provided between the vehicle body and a member that supports the steering column 6 that supports the steering wheel 1 with respect to the vehicle body so that it can break away in the forward direction due to an impact load in the forward direction during a secondary collision, and displaces in the forward direction together with the steering column 6.
FIG. 18 to FIG. 20 illustrate an example of this kind of steering apparatus. A housing 10, which houses the reduction gear and the like of an electric power steering apparatus, is fastened to the front end section of a steering column 6a. A steering shaft 5a is supported on the inside of the steering column 6a such that it can only rotate freely, and a steering wheel 1 (see FIG. 17) can be fastened to the portion on the rear end section of this steering shaft 5a that protrudes from the opening on the rear end of the steering column 6a. The steering column 6a and the housing 10 are supported by a bracket on the vehicle side (not shown) having a flat shape that is fastened to the vehicle body so that they can break away in the forward direction due to an impact load in the forward direction.
To accomplish this, a bracket 12 on the column side that is supported in the middle section of the steering column 6a and a bracket 13 on the housing side that is supported by the housing 10 are supported with respect to the vehicle body so that they both can break away in the forward direction due to an impact load in the forward direction. These brackets 12, 13 both comprise installation plate sections 14a, 14b at one or two locations, and notch sections 15a, 15b are formed in these installation plate sections 14a, 14b so that they are open on the rear end edges. With these notch sections 15a, 15b covered, sliding plates 16a, 16b are assembled in the portions of the brackets 12, 13 near both the left and right ends.
These sliding plates 16a, 16b are formed by bending thin metal plate such as carbon steel plate or stainless steel plate provided with a layer of a synthetic resin that slides easily, such as polyamide resin (nylon), polytetrafluoroethylene resin (PTFE) or the like on the surface into a U shape, having a top plate section and a bottom plate section that are connected by a connecting plate section. Through holes for inserting bolts or studs are formed in portions of the top and bottom plate sections that are aligned with each other. With these sliding plates 16a, 16b mounted on the installation plate sections 14a, 14b, the through holes are aligned with the notch sections 15a, 15b that are formed in these installation plate sections 14a, 14b. 
The bracket 12 on the column side and the bracket 13 on the housing side are supported by the bracket 11 on the vehicle side by screwing nuts onto bolts or studs that are inserted through the notch sections 15a, 15b in the installation plate sections 14a, 14b and the through holes in the sliding plates 16a, 16b, and tightening the nuts. During a secondary collision, the bolts or studs come out from the notch sections 15a, 15b together with the sliding plates 16a, 16b, which allows the steering column 6a and the housing 10 to displace in the forward direction together with the bracket 12 on the column side, the bracket 13 on the housing side and the steering wheel 1.
Moreover, in the example in the figure, energy absorbing members 17 are provided between the bolts or studs and the bracket 12 on the column side. As this bracket 12 on the column side displaces in the forward direction, the energy absorbing members 17 plastically deform so as to absorb the impact energy that is transmitted to the bracket 12 on the column side by way of the steering shaft 5a and steering column 6a. 
During a secondary collision, the bolts or studs, which was in a normal state shown in FIG. 19, come out from the notch sections 15a as shown in FIG. 20, which allows the bracket 12 on the column side to displace in the forward direction, and the steering column 6a displaces in the forward direction together with this bracket 12 on the column side. When this happens, the bracket 13 on the housing side also breaks away from the vehicle body, and is allowed to displace in the forward direction. As the bracket 12 on the column side displaces in the forward direction, the energy absorbing members 17 plastically deform and absorb the impact energy that is transmitted from the driver's body to the bracket 12 on the column side by way of the steering shaft 5a and the steering column 6a, which lessens the impact applied to the body of the driver.
In the case of the construction illustrated in FIG. 18 to FIG. 20, the bracket 12 on the column side is supported by the bracket 11 on the vehicle side at two locations, on both the right and left side, so that it can break away in the forward direction during a secondary collision. From the aspect of stable displacement in the forward direction without causing the steering wheel 1 to tilt, it is important during a secondary collision, that the pair of left and right support sections be disengaged at the same time. However, tuning in order that these support sections disengage at the same time is affected not only by resistance such as the friction resistance and the shear resistance to the disengagement of these support sections, but unbalance on the left and right of the inertial mass of the portion that displaces in the forward direction together with the steering column 6a, so takes time and trouble.
In order to stabilize the breaking away of the steering column in the forward direction during a secondary collision, applying the construction disclosed in JP51-121929(U) can be somewhat effective. FIG. 21 to FIG. 23 illustrate the construction disclosed in JP51-121929(U). In the case of this construction, a locking notch 18 is formed in the center section in the width direction of a bracket 11 on the vehicle side that is fastened to and supported by the vehicle body and that does not displace in the forward direction even during a secondary collision, and this locking notch 18 is open on the front end edge of the bracket 11 on the vehicle side. Moreover, a bracket 12a on the column side is supported by and fixed to the steering column 6a side such that it is able to displace in the forward direction together with a steering column 6b during a secondary collision.
Furthermore, both the left and right end sections of a locking capsule 19 that is fastened to this bracket 12a on the column side is locked in the locking notch 18. In other words, locking grooves 20 that are formed on both the left and right side surfaces of the locking capsule 19 engage with the edges on both the left and right sides of the locking notch 18. Therefore, the portions on both the left and right end sections of the locking capsule 19 that exist on the top side of the locking grooves 20 are positioned on the top side of the bracket 11 on the vehicle side on both side sections of the locking notch 18. When the bracket 11 on the vehicle side and the locking capsule 19 are engaged by way of the locking grooves 20 and the edges on both sides of the locking notch 18, locking pins 22 are pressure fitted into small locking holes 21a, 21b that are formed in positions in these members 11, 19 that are aligned with each other, joining the members 11, 19 together. These locking pins 22 are made using a relatively soft material such as an aluminum alloy, synthetic resin or the like that will shear under an impact load that is applied during a secondary collision.
When an impact load is applied during a secondary collision from the steering column 6b to the locking capsule 19 by way of the bracket 12a on the column side, these locking pins 22 shear. The locking capsule 19 then comes out in the forward direction from the locking notch 18, which allows the steering column 6b to displace in the forward direction together with the steering wheel 1 which is supported by this steering column 6b by way of the steering shaft 5.
In the case of the construction illustrated in FIG. 21 to FIG. 23, the engagement section between the locking capsule 19 that is fastened to the bracket 12a on the column side and the bracket 11 on the vehicle side is located at only one location in the center section in the width direction. Therefore, tuning for disengaging this engagement section and causing the steering wheel 1 to displace stably in the forward direction during a secondary collision becomes easy. Although this construction is effective from the aspect of allowing the steering column 6b to break away in the forward direction during a secondary collision with postural stability, in this construction, in order to more completely protect the driver by suppressing and stabilizing the load required for the disengagement (break away load), it is desired that the following points be improved.
In other words, in order to suppress the impact which is applied to the driver's body during a secondary collision more effectively, it is preferable to suppress the break away load so as to allow the steering column 6a to begin to be displaced in the forward direction at the instant of the secondary collision. In addition to facilitate the smooth displacement of the steering column 6a in the forward direction at the instant of the secondary collision, so as to suppress the impact which is applied to the driver's body who collides against the steering wheel 1, also after the beginning of the displacement of the steering column 6a, by plastically deforming an energy absorbing member 17 attached to the steering column 6a, the impact energy transmitted to the steering wheel 1 is absorbed, such that the protection for the driver can be enhanced.
In the case of the construction illustrated in FIG. 21 to FIG. 23, so as to allow the steering column 6a to begin to be displaced in the forward direction at the instant of the secondary collision, it is necessary to shear a plurality of locking pins. In order to shear these locking pins, a certain amount of the impact load is required, that is disadvantage for suppressing the break away load. On the other hand, in the construction shown in FIG. 18 to FIG. 20, tuning in order to stabilize the attitude of steering column 6a takes time and trouble, and a slight change in tightening torque of a bolt or the like for assembling the bracket 12 on the column side on the vehicle body side causes the break away load to vary widely, complicating the control of the tightening torque. For these reasons, in these conventional constructions, it is difficult to disengage this steering column 6a from the vehicle side in the forward direction with posture stability and decrease and stabilize the break away load.